Papermaking composition



Patented Sept. 29.19 31 {UNITED STATES. PATENT OFFICE GEORGE A.

RICHTER, OF BERLIN, NEW HAMPSHIRE, ASSIGNOR '10 BROWN COMPANY,

OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE runnmxnm oonrosrrron Io Drawing.

This invention relates to apermaking compositions, being more particularly concerned with compositions which may be used in making high grade papers having a combination of desirable characteristics heretofore unattained by the use of ordinary papermaking furnishes.

In making the hi hest grade writing and printing papers, it has been the practice to use, as raw material, stable, white fibers, such as rag pulps or wood pulps of high alpha cellulose content derived from woods such as spruce. Because the fibers, of such pulps are comparatively lon they interfelt well on the apermaking mac ine and, because they are ree from non-alpha cellulose impurities, the resulting papers are resistant to the deterioratin action of air, heat and light, possessing w at is known in the art as high permanenc or good ageing qualities.

Before ormmg into paper, long-'fibered stocks such as described must be treated in a manner to generate suflicient cellulose gel therein to impart the desired strength and folding endurance to the paper, as well as to reduce length of fiber sufliciently to result in a well-formed or closed in sheet. T0 attain these results,-the papermaker subjects the stock to the action of a beater engine until it has acquired the desired gelatinized condition or slowness, and then passes it through a Jordan engine. The Jordan engine cuts the fibers and so conditions them for improved paper formation, but the shortened fibers do not ofl'er as great resistance to tearing in the paper made therefrom as would the longfibered stock if employed as a raw material.

In accordance with the present invention, a subordinate proportion of stable, white pulp of short fiber len th is used along with longfibered stocks suc as hereinbefore described, as the use of such a mixture of fibers makes possible dispensing with or minimizing the use of a Jordan engine, and the production of well-formed papers of the desired strength, folding endurance, and of much higher tear resistance than that possessed by paper made from stock which has been passed through a Jordan engine. The short-fibered pulp which I employ may be derived from Application filed November 15, 1929. Serial No. 407,588.

short-fibered woods, such as poplar. It is essential that it be of high alpha cellulose content, as the use of ashort-fibered raw material such as soda pulp is disadvantageous in themanufacture of high grade papers,

owing to its high proportion of non-alpha cellulose constituents, such as pentosans. The alpha cellulose content of the usual commercial soda pulp is only about 83% to 85%, and its pentosan content is about 8% to 15%, which latter constituent, together with other impurities, renders the pulp unstable and unfit for use in high grade papers. The shortfibered wood pulp employed in the papermaking composition of the present invention is of high alpha cellulose and low pentosan content. It may be prepared from shortfibered woods, such as poplar, by a process such as follows. The Wood in chipped condition may be cooked in an acid sulphite liquor, for instance in the usual calcium base 1i uor containing1% combined and 5% free g0 or .in a sodium base liquor, to produce a cleaner and more easily bleachable pulp.

The cooking operation may be carried out at a temperature of about 275 to 285 F. for about nine to ten hours, during which time free SO may be released from the digester to maintain the pressure at about 75 pounds. The digester contents may then be blown into a pit, and the raw woodpulp may be separated from the spent liquor by washing in the usual manner. The raw pulp may be converted to a white product of high alpha cellulose content by'suitable-refining steps. To this end, it may initially be treated at room temperature for about two to three hours, with a liquor containin about 1% to 3% chlorine or 1% to 5% hypoc lorite bleach, based on the dry weight of pulp. Or, if desired, both a suitable chlorine water treatment and hypochlorite bleach liquor treatment may be employed. 1 The chlorine water and/or bleach liquor removes lignin and other coloring matter from the pulp, or renders such matter soluble in alkaline liquors. The pulp is then washed, whereupon it may be treated with an alkaline liquor to remove chlorine reaction products and other nonalpha cellulose constituents from the pulp.

that when mixed with long-fi For instance, the ulp maybe treated at about 100 C. or at hig or temperature and under super-atmospheric pressure for about four to six hours, with a solution containing about 10% to 12% caustic soda, based on the weight of dry pulp. Or, if desired, the treatment may be effected at lower temperature with a more concentrated caustic soda solution, for instance at from 20 to 40 (1., for about two hours, in a solution containing 50% caustic soda, based on the weight of dry pulp. The refined pulp may then be bleached with a suitable agent to the desired whiteness, for instance, with calcium orsodium hypochlorite bleach liquor, preferably containin sufiicient free alkali to ensure a condition 0 distinct alkalinity throughout the bleaching operation, as such a condition prevents the formation of oxycellulose and accordingly results in a white product of maximum alpha cellulose content and stability. If desired, a permanganate bleach liquor may be employed, in which case the liquor should be maintained neutral or acid, in order to avoid degradation of fiber into oxycelluloses.

The resulting product is extremely free and resistant to gelatinization bgebeatmg, so red stocks such as rag pulp or long-fibered wood ulps, and beaten, it retains its opacity and bul iness' and imparts these characteristics and better printing properties to the resultin In either beaten or unbeaten con ition, it shrinks and swells much less than .do the long fibers, and accordingly may be used to advantage in admixture with the long fibers to produce papers which undergo much less change in dimensions when exposed to varying humidit conditions or when immersed in aqueous bat s and then dried, than papers heretofore produced. This property of the fiber renders it especially valuable for use in the manufacture of blueprint and photographic papers, which are subjected to such conditions.

In producing papermakin com ositions, the short-fibered pulps may e ad ed in desired fproportion, say 10% to 25%, to suitable longbered stock, such as rag pulp or wood 'pulp of high alpha cellulose content derived rom long-fibere'd woods such as spruce, either before or after the long-fibered stock has been subjected to beating to produce cellulose gel in suflicient amount to impart the desired strength and folding endurance to the resultin paper. Excellent results may be obtaine when the unbeaten, shortfibered pulp is added after the long-fibered stock has been beaten to the desired slowness, as in such case the short-fibered portion may be incorporated throughout the beaten and "elatinized long-fibered portion, with the beater roll sufiiciently raised from the bedplate of the beater engine to effect merely a mixing of the fibers. The composition may aper..

'of excellent formation and having excel ent stability, strength, folding endurance, tear resistance, bulk, and opaqueness.

I. claim: I

1. A papermaking composition comprisin a stable, white, long-fibered pulp of hig alpha cellulose content in elatinized condition, and a stable, white, s ort-fibered wood pulp of high alpha cellulose content in free condition.

.2. A apermaking composition, com rising a sta 1e, white, long-fibered pul of igh alpha. cellulose content and a su ordinate pro 'ortion of stable, white, poplar pulp of 'g alpha cellulose content.

3. A process which comprises forming a mixture of stable, white, long-fibered pulp of high alpha cellulose content in gelatimzed condition and stable, white, short-fibered wood pulp of high alpha cellulose content in free condition; and running off the m1xture into paper.

4. A process which comprises beating a stable, white lo'ng-fibered pulp to the desired slowness; mixin a subordinate proportion of unbeaten, stab e, white, poplar pulp therewith; and running off the mixture into paper.

5. Apapermakm composition comprising a blend of two cel ulose pulps, both being stable, white pulps of high alpha cellulose content, but one being derived from a longfibered cellulosic source, and the other being derived from a short-fibered cellulosic source. 6. Apapermakin composition comprising a blend of two woo pulps, both being stable, white pulps of high alpha cellulose content, but one being derived from a long-fibered wood of the type of spruce, and the other being derived from a short-fibered wood of the type of poplar.

In testimony whereof I have affixed my signature.

' GEORGE A. RICHTER. 

